A bicyclo[2.2.2]octylamine derivative represented by the following general formula (8) is important as a raw material for preparing pharmaceutical products such as drugs for treating diabetes (Patent Documents 1 to 3):
[in the formula (8), R1 represents an alkyl group having 1 to 6 carbon atoms, which may have a substituent; an arylmethyl group which may have a substituent; or an arylethyl group which may have a substituent; and
R3 represents a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, which may have a substituent, or an aralkyl group which may have a substituent.
In Patent Documents 1 to 3, the bicyclo[2.2.2]octylamine derivative is prepared from, for instance, a bicyclo[2.2.2]octyldicarboxylic acid derivative. However, these Patent Documents 1 to 3 do not disclose, at all, the process for preparing a bicyclo[2.2.2]octylamine derivative by forming the bicyclo[2.2.2]octane skeleton while simultaneously linking an amine compound to the skeleton.
Non-Patent Documents 1 to 6 disclose processes for preparation of bicyclo compounds.
However, Non-Patent Document 1 relates to a process for preparation of a bicyclo[2.2.2]octyldicarboxylic acid derivative by reacting cyclohexyl-1,4-dicarboxylate with 1-bromo-2-chloroethane and does not relate to a process for preparing a bicyclo[2.2.2]octylamine derivative using an amine compound. For this reason, the process of Non-Patent Document 1 requires the use of a reaction to be carried out at low temperature and accordingly, this process should use quite expensive reagents.
Non-Patent Documents 2 and 6 also disclose processes for reducing the carbonyl group of a bicyclo[2.2.2]octane skeleton after the formation of the latter. In these articles, the carbonyl group is reduced after it is converted into a dithiane derivative or a dithiolane derivative.
The techniques disclosed in Non-Patent Documents 3 and 5 relate to processes for preparing bicyclo[2.2.2]octylamine derivatives, in which a secondary amine compound is linked to a bicyclo[2.2.2]octane skeleton simultaneous with the formation of the latter. However, these prior articles never disclose the process for preparation of a bicyclo[2.2.2]octylamine derivative by the linkage of a primary amine compound to such a bicyclo[2.2.2]octane skeleton.
Even in Non-Patent Document 4, there is disclosed a process for formation of a bicyclo[2.2.2]octyl skeleton, but this article does not disclose the process for preparing a bicyclo[2.2.2]octylamine derivative by forming the bicyclo-[2.2.2]octane skeleton while simultaneously linking an amine compound to the skeleton.